1. Field of the Invention
This invention relates to oil well service equipment, particularly to a device for moving pipe into or out of a well. The invention is particularly designed to allow one to raise or lower pipes having large collars or tools through a multiple-bowl support.
2. Description of the Prior Art
Pipes used in oil wells, either during drilling or during production of the well, are generally made up from sections of pipe about thirty feet long. A string of such sections is formed by lowering the string by means of an elevator to near the drilling rig deck surface, then securing the string with slips in a structure at the deck surface (to keep the pipe from falling into the well). At this point, a new section of pipe is threaded to the upper end of the existing string, the elevator is raised and engaged with the upper end of the new section, the slips in the supporting structure are released, and the elevator lowered. This cycle is repeated until a string of desired length--often thousands of feet--is formed. A large variety of supports for carrying out this operation are known.
It is often desired to provide a well with more than one pipe string. For this purpose, there are multiple-pipe supports and elevators. Particularly with such devices, the insertion of large-diameter tools and collars into the well is problematic, because the multiple pipe supports tend to obstruct the well opening. Although the pipes can be temporarily supported well above the deck surface by the elevator, it would be desirable to expose an opening in the supporting device equal to the diameter of the well casing, so that large tools and the like could be inserted. This problem has been recognized: for example, U.S. Pat. No. 3,071,396 provides a device with an enlarged central portion, which permits passage of larger couplings.
None of the prior devices is wholly satisfactory, for various reasons. The need remains for a multiple-pipe support device that can be readily and remotely "opened" to permit large elements to enter or leave the well.